I would connect the Empeg to your computer directly for testing. I've had two 10/100 switches (D-Link and Linksys) at my office that would cause data loss. Currently we are using a 16 port 10 Mbit hub and there havn't been problems since.

I don't think that the problem is switch vs. hub since I use a clearance-bin CompUSA 10/100 switch at my house and it works like a charm. Rather, I think there are many cheap switches out there that are poorly designed.

Also, if you are using a home-made cable I would suggest using PVC if it's not going to create a fire hazard. I find that the crimp holds to the PVC cables a lot better than plenum because of the (usually) thicker jacket.